We have had the Sigma sprayer since 11/07. It works GREAT and is very easy to install.

We bought it from Ebay (I believe it cost just under $30 with free shipping) from the Sigma store.

It's been installed, uninstalled and reinstalled again several times (we moved once and we've had two bathrooms in each location and at one point or another, we've moved the sprayer between the two bathrooms for whatever reason), without issue.